feat(admin): separate platform CRUD from CMS, add entity selector macro

- Move platforms menu from CMS to Platform Admin section with create/edit
- Add platform create page, API endpoint, and service method
- Remove CMS-specific content from platform list and detail pages
- Create shared entity_selector + entity_selected_badge Jinja macros
- Create entity-selector.js generalizing store-selector.js for any entity
- Add Tom Select merchant filter to stores page with localStorage persistence
- Migrate store-products page to use shared macros (remove 53 lines of duped CSS)
- Fix broken icons: puzzle→puzzle-piece, building-storefront→store, language→translate, server→cube

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/modules/tenancy/static/admin/js/platform-create.js

@@ -0,0 +1,134 @@
+/**
+ * Platform Create - Alpine.js Component
+ *
+ * Handles platform creation for multi-platform CMS.
+ */
+
+const platformCreateLog = window.LogConfig.createLogger('PLATFORM_CREATE');
+
+function platformCreate() {
+  return {
+    // Inherit base layout functionality from init-alpine.js
+    ...data(),
+
+    // Page identification
+    currentPage: 'platform-create',
+
+    // State
+    saving: false,
+    error: null,
+
+    // Language editing
+    currentLang: 'fr',
+    languageNames: {
+      fr: 'Fran\u00e7ais',
+      de: 'Deutsch',
+      en: 'English',
+      lb: 'L\u00ebtzebuergesch',
+    },
+
+    // Form data
+    formData: {
+      code: '',
+      name: '',
+      description_translations: { fr: '', de: '', en: '', lb: '' },
+      domain: '',
+      path_prefix: '',
+      default_language: 'fr',
+      supported_languages: ['fr', 'de', 'en', 'lb'],
+      is_active: true,
+      is_public: true,
+    },
+
+    errors: {},
+
+    // Available languages
+    availableLanguages: [
+      { code: 'fr', name: 'French' },
+      { code: 'de', name: 'German' },
+      { code: 'en', name: 'English' },
+      { code: 'lb', name: 'Luxembourgish' },
+    ],
+
+    // Lifecycle
+    async init() {
+      platformCreateLog.info('=== PLATFORM CREATE PAGE INITIALIZING ===');
+
+      // Duplicate initialization guard
+      if (window._platformCreateInitialized) {
+        platformCreateLog.warn('Platform create page already initialized, skipping...');
+        return;
+      }
+      window._platformCreateInitialized = true;
+
+      platformCreateLog.info('=== PLATFORM CREATE PAGE INITIALIZATION COMPLETE ===');
+    },
+
+    async handleSubmit() {
+      this.saving = true;
+      this.error = null;
+      this.errors = {};
+
+      try {
+        // Sync base description from default language translation
+        const defaultLang = this.formData.default_language || 'fr';
+        const baseDesc = this.formData.description_translations[defaultLang] || '';
+
+        const payload = {
+          code: this.formData.code,
+          name: this.formData.name,
+          description: baseDesc || null,
+          description_translations: this.formData.description_translations,
+          domain: this.formData.domain || null,
+          path_prefix: this.formData.path_prefix || null,
+          default_language: this.formData.default_language,
+          supported_languages: this.formData.supported_languages,
+          is_active: this.formData.is_active,
+          is_public: this.formData.is_public,
+        };
+
+        const response = await apiClient.post('/admin/platforms', payload);
+
+        platformCreateLog.info(`Created platform: ${response.code}`);
+
+        // Redirect to the new platform's detail page
+        window.location.href = `/admin/platforms/${response.code}`;
+      } catch (err) {
+        platformCreateLog.error('Error creating platform:', err);
+        this.error = err.message || 'Failed to create platform';
+
+        // Handle validation errors
+        if (err.details) {
+          this.errors = err.details;
+        }
+      } finally {
+        this.saving = false;
+      }
+    },
+
+    // Helper Methods
+    isLanguageSupported(code) {
+      return this.formData.supported_languages.includes(code);
+    },
+
+    toggleLanguage(code) {
+      const index = this.formData.supported_languages.indexOf(code);
+      if (index > -1) {
+        // Don't allow removing the last language
+        if (this.formData.supported_languages.length > 1) {
+          this.formData.supported_languages.splice(index, 1);
+          // Switch tab if the removed language was active
+          if (this.currentLang === code) {
+            this.currentLang = this.formData.supported_languages[0];
+          }
+        }
+      } else {
+        this.formData.supported_languages.push(code);
+        // Initialize empty translation for new language
+        if (!this.formData.description_translations[code]) {
+          this.formData.description_translations[code] = '';
+        }
+      }
+    },
+  };
+}